1. Field of the Invention
The present invention relates to an improvement to the invention described in co-pending application Ser. No. 952,071 of Jean-Jacques Binder, filed Oct. 17, 1978, entitled "A Particle Feed Arrangement for Applying Solid Particles to the Image Carrier of a Non-Impact Printer" and corresponding to French patent application No. 77 31966, filed Oct. 24, 1977. It relates in particular to a solid particle conveying member, which conveys solid particles into the vicinity of the surface of an image carrier of a non-impact printer.
2. Description of the Prior Art
So called non-impact or strikeless transfer printing machines are known in which characters are printed without relying for this purpose on the impact of raised printing type against a recipient sheet of paper.
Printing machines of this kind generally have an image carrier which is usually formed by a rotary drum or an endless belt on the surface of which sensitized zones, also termed latent images, can be formed, by electrostatic or magnetic methods, which correspond to the characters or images to be printed. The latent images are then developed, that is to say, rendered visible, by means of a powder developing pigment which, when deposited on the image carrier, is only attracted by its sensitized zones. After this, the particles of pigment which have been deposited in this way on the latent images are transferred to a carrier sheet, such as a sheet of paper, for example, to which they are then permanently affixed.
In the prior art, various particle applicator arrangements have been used to apply the powdered developing pigment to the image carrier of a printing machine of this kind. For example, use has been made of an arrangement which incorporates a cylindrical casing containing the powdered pigment. This casing is provided with an opening across which the image carrier passes. The carrier is supplied with pigment by a cylindrical brush, which, as it rotates within the casing, throws particles of pigment onto the surface of the carrier as the latter passes across the opening. This arrangement is not entirely satisfactory in use owing, on the one hand, to the fact that it causes a cloud of pigment particles to be formed which spreads outside the casing, which is particularly unpleasant for people who, being near the printer, come into contact with the cloud, and on the other hand, to the fact that the particles become electrified in an undesirable way and, when thrown onto the carrier, are able to cling to the unsensitized zones of the carrier as a result of electrostatic attraction.
The particle applicator arrangement which is described in the aforenoted application for patent overcomes these disadvantages. That arrangement includes on the one hand, a conveying member which is arranged to feed the particles of pigment from a source tank into the vicinity of the surface of the carrier and on the other hand, a deflector interposed between the carrier and the conveying member to collect the particles conveyed by this member. The deflector has one of its edges arranged in the immediate vicinity of the said carrier in such a way as to form, in conjunction with the carrier, a trough substantially in the shape of a dihedral prism in which the particles so collected build up. Because of this, when the image carrier moves in the appropriate direction to carry the particles which have built up towards the edge of the trough, the particles which are carried past this edge remain applied only to the sensitized zones of the said image carrier and excess non-applied particles are returned to the source.